LM5575EVAL

User's Guide SNVA209C – January 2007 – Revised April 2013 AN-1569 LM5575 Evaluation Board 1 Introduction The LM5575 evaluation board is designed to provide the design engineer with a fully functional power converter based on emulated current mode control to evaluate the LM5575 regulator IC. The evaluation board provides a 5V output with a 1.5A current capability. The ultra-wide input voltage ranges from 7V to 75V. The design operates at 300kHz, a good compromise between conversion efficiency and solution size. The printed circuit board consists of 2 layers of 2 ounce copper on FR4 material with a thickness of 0.06 inches. This application note contains the evaluation board schematic, Bill-of-Materials (BOM) and a quick setup procedure. Refer to the LM5575 75V, 1.5A Step-Down Switching (SNVS471) data sheet for complete circuit design information. The performance of the evaluation board is as follows: Input Range: 7 to 75V Output Voltage: 5V Output Current: 0 to 1.5A Frequency of Operation: 300 KHz Board Size: 2.6 X 1 X 0.4 inches Load Regulation: 1% Line Regulation: 0.1% Over Current Limiting All trademarks are the property of their respective owners. SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated AN-1569 LM5575 Evaluation Board 1 Evaluation Board Schematic www.ti.com 2 Evaluation Board Schematic 3 Powering and Loading Considerations Read this entire page prior to attempting to power the evaluation board. 3.1 Quick Setup Procedure Step 1: Set the power supply current limit to 1.8A. Turn off the power supply. Connect the power supply to the Vin terminals. Step 2: Connect the load, with a 1.5A capability, to the Vout terminals. Positive connection to J2 and negative connection to J3. Step 3: The SD pin should be left open for normal operation. Step 4: Set Vin to 24V with no load applied. Vout should be in regulation with a nominal 5V output. Step 5: Slowly increase the load while monitoring the output voltage, Vout should remain in regulation with a nominal 5V output as the load is increased up to 1.5 Amps. Step 6: Slowly sweep the input voltage from 7 to 75V, Vout should remain in regulation with a nominal 5V output. Step 7: Temporally short the SD pin to GND to check the shutdown function. Step 8: Increase the load beyond the normal range to check current limiting. The output current should limit at approximately 2.1A. The power supply (Vin source) current limit may need to be increased for this step. Cooling is critical during this step. 3.2 Air Flow Prolonged operation with high input voltage at full power will cause the thermal shutdown circuit within the regulator IC to activate. A stand-alone fan with at lease 200 LFM should always be provided. 2 AN-1569 LM5575 Evaluation Board SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Performance Characteristics www.ti.com 3.3 Powering Up Using the shutdown pin provided will allow powering up the source supply with the current level set low. It is suggested that the load be kept low during the first power up. Set the current limit of the source supply to provide about 1.5 times the anticipated wattage of the load. As you remove the connection from the shutdown pin to ground, immediately check for 5 volts at the output. A quick efficiency check is the best way to confirm that everything is operating properly. If something is amiss you can be reasonably sure that it will affect the efficiency adversely. Few parameters can be incorrect in a switching power supply without creating losses and potentially damaging heat. 3.4 Over Current Protection The evaluation board is configured with over-current protection. The output current is limited to approximately 2.1A. The thermal stress is quite severe while in an overloaded condition, limit the duration of the overload and provide sufficient cooling (airflow). 3.5 Synchronization A SYNC pin has been provided on the evaluation board. This pin can be used to synchronize the regulator to an external clock or multiple evaluation boards can be synchronized together by connecting their SYNC pins together. Refer to the LM5575 datasheet for complete information. 4 Performance Characteristics Efficiency Plots Figure 1 shows the conversion efficiency versus output current for several input voltage conditions. 100 90 EFFICIENCY (%) 80 70 60 VIN = 24V 50 VIN = 7V VIN = 48V 40 30 VIN = 75V 20 10 0 0.25 0.5 0.75 1 1.25 1.5 IOUT (A) Figure 1. Efficiency Plots Turn-on Waveform When applying power to the LM5575 evaluation board a certain soft-start sequence occurs. Figure 2 shows the output voltage during a typical start-up sequence. SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated AN-1569 LM5575 Evaluation Board 3 Performance Characteristics www.ti.com Conditions: Input Voltage = 36VDC, Output Current = 1A Trace 1: Output Voltage Volts/div = 2V Horizontal Resolution = 500 µsec/div Figure 2. Turn-On Waveform Output Ripple Waveform Figure 3 shows the output voltage ripple. This measurement was taken with a very short ground clip and 20MHZ bandwidth limiting. Conditions: Input Voltage = 36VDC Output Current = 1A Bandwidth Limit = 20 MHz Trace 1: Output Ripple Voltage Volts/div = 50 mV Horizontal Resolution = 2 µsec/div Figure 3. Output Ripple Waveform 4 AN-1569 LM5575 Evaluation Board SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Layout and Bill of Materials www.ti.com 5 Layout and Bill of Materials The Bill of Materials is shown in Table 1, including the manufacturer and part number. Table 1. 5V, 1.5A Demo Board Bill of Materials Item Part Number Description Value C 1 C3225X7R2A105M CAPACITOR, CER, TDK 1µ, 100V C 2 C3225X7R2A105M CAPACITOR, CER, TDK 1µ, 100V C 3 C0805A471K1GAC CAPACITOR, CER, KEMET 470p, 100V C 4 C2012X7R2A103K CAPACITOR, CER, TDK 0.01µ, 100V C 5 C2012X7R2A103K CAPACITOR, CER, TDK 0.01µ, 100V C 6 OPEN NOT USED C 7 C2012X7R2A223K CAPACITOR, CER, TDK 0.022µ, 100V C 8 C2012X7R1C474M CAPACITOR, CER, TDK 0.47µ, 16V C 9 C3225X7R1C106M CAPACITOR, CER, TDK 10µ, 16V C 10 APXE6R3ARA121ME61G CAPACITOR, AL, NIPPON 120µ, 6.3V C 11 C0805C331G1GAC CAPACITOR, CER, KEMET 330p, 100V C 12 OPEN NOT USED D 1 CMSH3-100 DIODE, 100V, CENTRAL L 1 DR125-470 INDUCTOR, COOPER R 1 OPEN NOT USED R 2 OPEN NOT USED R 3 CRCW08052102F RESISTOR 21kΩ R 4 CRCW08054992F RESISTOR 49.9kΩ R 5 CRCW08055111F RESISTOR 5.11kΩ R 6 CRCW08051651F RESISTOR 1.65kΩ R 7 CRCW2512100J RESISTOR 10, 1W U 1 LM5575 REGULATOR, Texas Instruments SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated 47µH AN-1569 LM5575 Evaluation Board 5 PCB Layout 6 www.ti.com PCB Layout Figure 4. Component Side Figure 5. Solder Side 6 AN-1569 LM5575 Evaluation Board SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated PCB Layout www.ti.com Figure 6. Silkscreen SNVA209C – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated AN-1569 LM5575 Evaluation Board 7 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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